The "hmc833_frac_fb.txt" file configures the HMC833 to work with onboard 50MHz reference. I've attached a file you can use with 10MHz reference. This file changes "XTAL 50" to "XTAL 10" which initializes the GUI to perform all frequency calculations assuming 10MHz reference. You can make this same change from the main GUI after clicking "Update":

Now clicking "Update Frequency" sends the correct N divider setting to the HMC833. You cannot just connect an external 10MHz reference to J5 without making a few modifications to disable the onboard 50MHz source and HMC1031 jitter cleaner.

The original file configures the lock detector for operation with 50MHz comparison frequency. You may notice the lock detector indicates an out-of-lock condition when in fact the part is locked. To fix this the "hmc833_frac_fb_10MHz" file sets Reg 0x07 to 0x24D instead of 0x14D. You can make the same change using "SPI Read/Write 1" from the main GUI and writing 0x24D into register 7: